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Bridge Corrosion Wiki
'Welcome to the Wiki' Welcome to the bridge corrosion wiki. This wiki page represents the work of Group #17 of CHEM 409. 'Introduction to Bridge Corrosion' Bridges have been around for a long time. The first bridges existed in nature, simply as Bridges have been around for a long time. The first bridges existed in nature, simply a fallen log spanning two points. Humans originally built bridges from wood but eventually turned to stone and concrete as materials. Iron started to become widely used for bridges in the 19th century.1 During the industrial revolution, it became more financially viable to produce and was used for its tensile strength to support large loads unlike stone or concrete. The first cast iron bridge was built in Coalbrookdale in 1779. In the early 1800s, cast iron was beginning to be replaced by wrought iron and until 1840, the construction material used was either cast iron or wrought iron or a combination of both. In the late 1800s, steel began to replace wrought iron due to its superior tensile strength and ductility.2 Bridges are important infrastructures necessary for the facilitation of goods and population. Iron corrosion in bridges is important to investigate because corrosion can have a negative effect on the integrity of the bridge and this can lead to catastrophic events. Corrosion can have a significant economic impact with the need of replacement or rehabilitation of the bridges.3 Corrosion can be classified in two different classes: generalized corrosion and localized corrosion. Whereas generalized corrosion attacks the whole metal that is unsheltered to the corrosive substance, localized corrosion attacks specific localized areas.10 This page is dedicated to looking at the chemistry of iron corrosion, solutions to remedy the problem and its evaluation, and the future directions of preventive and rehabilitation methods. 'Why is it a problem?' Bridges have become an essential part of developed society. The US alone has approximately 603,310 bridges that link more than 4 million miles of roadways.7 Corrosion is one of the major causes of bridge damage and failure. The most obvious reason is the weakening of metal elements in a bridge due to corrosion. However if the corroding metal is a reinforcing bar contained in concrete, a commonly used technique in bridge building, it will also compromise the concrete’s stability. The products of corrosion occupy a larger volume than the original metal, for iron up to 6 times as much volume depending on oxidation state and the amount of water included in the product (Fig. 6). This increase in volume is restrained by the presence of the reinforcing bar itself and leads to the creation of tensile stresses. As concrete has a very low tensile strength this will lead to material failure of the concrete, usually resulting in the formation of cracks in the bridge element.8 The maintenance or replacement of corrosion-damaged bridges has significant economic implications. A 2002 study showed that the US spends about $8.3 billion in bridge repair annually. This includes costs of minor maintenance such as repainting of protective coatings as well as partial and complete replacements of bridge elements and complete structures (Fig. 2). However, the consequences of the corrosion are not limited to government expenditure- it can also affect the public in a more direct way. The failure, construction and maintenance of corroded bridges can over time increase the wear and tear of automobiles and negatively impact their fuel efficiency. And of course in extreme cases, structurally deficient bridges pose a great risk to public safety and bridge closures results in transportation delays.9 'More Information' *'Case Studies' *'Chemical Mechanisms' *'Solution to Problem' *'Future Direction' *'References' Category:Browse